Ultralow Pt amount of Pt-Fe alloys supported on ordered mesoporous carbons with excellent methanol tolerance during oxygen reduction reaction

摘要

The synthesis of ordered mesoporous carbons supported various atomic ratios of Pt-Fe nanoparticles (PtxFe100-x/OMC) with low Pt loading and high Pt-Fe alloying extent is reported. The resultant PtxFe100-x/OMC have been thoroughly characterized by a variety of different spectroscopic techniques and used as electrocatalysts during oxygen reduction reaction (ORR) for direct methanol fuel cell (DMFC) at cathode. Results obtained from X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the Pt metal in the PtxFe100-x/OMC is formed in the face-centered cubic (fcc) crystalline structure and composed of Pt(0) and Pt oxides. By using N-2 adsorption/desorption isotherms, transmission electron microscopy (TEM), it was found that Pt-Fe alloy nanoparticles (3-5 nm) homogeneously dispersed on the mesoporous carbon supports with high surface areas (>1000 m(2) g(-1)) and regular pore channels (ca. 3.4 nm) for all PtxFe100-x/OMC. Further studies by X-ray absorption spectroscopy (XAS) reveal that the Pt-rich(shell)-Fe-rich(core) microstructure with a higher Pt-Fe alloying state is accountable for the superior ORR performance observed for the PtxFe100-x/OMC, as compared to the commercial electrocatalysts. Among the various PtxFe100-x/OMC catalysts, the Pt45Fe55/OMC exhibits the highest ORR performance, methanol-tolerant capability and ultralow Pt content, which should have potential applications as cathodic catalysts in DMFC. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.